Non-contact ultrasonic imaging of post-tensioned bridges to investigate corrosion and void status

Corrosion of the nation's transportation infrastructure is a widespread and costly problem. Recent corrosion problems in post-tensioned bridge structures (Figure 1) have increased the need for a reliable method for determining grout voids and level of corrosion in post-tensioned tendons. Corrosion monitoring techniques such as half-cell potential and corrosion rate measurements face problems when used in this type of structure and standard NDE (non-destructive evaluation) methods such as impact-echo have also encountered problems. This study begins the evaluation of a method called C-Scan ultrasonic imaging to evaluate grouted post-tensioned tendons. While this paper focuses on post-tensioning applications, the C-Scan technique may be valuable for investigation of any type of reinforced concrete structure.